The sum will come from funds earmarked for important national projects under the country's public investment plan 2016-2020, the government said in its proposal.

The expressway, which connects the capital with the northern port city, was finished in 2015 in the form of a build-operate- transfer (BOT) project, at a cost of VND45 trillion ($2 billion).

The government needed to invest 30-50 percent of that amount, or VND13-22 trillion ($556-941 million), while the rest would come from the investor, Vietnam Infrastructure Development and Finance Investment Jsc (VIDIFI), who would collect tolls on the expressway to recover investment.

But as the government’s budget was limited at that time, it promised to pay the money with land use fees and rentals collected in urban areas and industrial zones built near the expressway after the project was completed.

The government was supposed to pay VIDIFI over VND4 trillion ($171 million) for land clearance, VND4.7 trillion ($201 million) from land use fees of the Gia Lam Urban Area in Hanoi near the expressway, and another $300 million for a loan VIDIFI had acquired from a South Korean and a German bank.

But the firm has not received any of this money. VIDIFI said in a recent statement that as of last year it has to pay interest mounting to over VND800 billion ($34.2 million) on loans due to the government's payment delay.

"If the government won’t pay the debt, we might have to declare bankruptcy."

The Hanoi – Hai Phong Expressway is among Vietnam's biggest transport infrastructure projects. According to VIDIFI, it serves over 27,000 vehicles each day on six lanes that allows speeds of up to 120 kilometers an hour.